This invention relates to shoes and, more particularly, to athletic shoes having internal midsoles.
A typical athletic shoe includes a durable rubber outsole, a midsole overlying the outsole, an upper secured to a top surface of the midsole, and a thin sock liner (insole) inside the upper. The midsole is generally made of a resilient foam material, such as ethylene vinyl acetate (EVA) or polyurethane (PU), which provides cushioning and support to the shoe wearer's foot. Typically, construction of the upper involves stitching and gluing together multiple pieces of leather and textiles that constitute the upper. Typically, the upper includes a flat, thin, relatively rigid lasting board that defines the bottom surface of the upper. Formation of the upper (referred to in the art as "lasting") allows the upper to take the approximate shape of the shoe wearer's foot. The lasting board is designed to maintain the proper bottom dimensions of the upper during the lasting process. After the upper has been lasted, it is cemented or otherwise bonded to an upper surface of the midsole. A lower surface of the midsole is cemented or otherwise bonded to an upper surface of the outsole. Finally, a sock liner or insole is placed into the interior of the upper on top of the lasting board. The sock liner is usually necessary for comfort because, without it, the shoe wearer's foot would rest directly on the rigid lasting board.
A disadvantage of many prior art athletic shoes is that, over time, the midsoles become worn rather quickly through compaction of the foam material. This greatly reduces the cushioning capacity of the shoe since the midsole is most often the primary cushioning component in athletic footwear. EVA midsoles may compress to as little as 50% of their original thickness after shoes have been worn for less than a month. It is then necessary to replace to entire shoe if optimum performance is desired since the midsoles are cemented or otherwise bonded to the other components of the shoe.
Another disadvantage of many prior art athletic shoes is that there is no opportunity for customization. Midsoles that provide adequate shock absorption for one shoe wearer may fail to provide adequate shock absorption for a heavier shoe wearer. Also, midsoles that provide adequate shock absorption for a shoe wearer in one type of activity may be inappropriate for another type of activity. Accordingly, there is a need for an athletic shoe having a construction that enables the shoe wearer to remove and replace the midsole of the shoe.